Process for preparation of modified polyphenylene ether or related polymers and the use thereof in modified high temperature rigid polymer of vinyl substituted aromatics

ABSTRACT

Process for the manufacture of modified polyphenylene ether or structurally related polymers comprising: 
     the reaction of polyphenylene ether or structurally related polymer with a non-cyclic acid anhydride, in the presence of a pyridine derivative substituted by an amine group as catalyst, and in a vinyl substituted aromatic monomer as solvent; 
     modified polyphenylene ethers so obtained and use of them for the manufacture of modified high temperature rigid poly (vinyl substituted aromatic) polymer compositions.

The invention relates to a process for the preparation of modifiedpolyphenylene ether or related polymers and to the use thereof inmodified high temperature rigid polymers of vinyl substituted aromatics.More particularly the invention relates to an improved process for thepreparation of modified polyphenylene ether or structurally relatedpolymers by capping the residual free hydroxy groups in such compoundsby reaction with an acid derivative.

Blends of polymers of vinyl substituted aromatics andpoly(2,6-dimethyl-1,4-phenylene ether), furtheron to be indicated byPPE, or structurally related polymers and more particularly blends ofpolystyrene and PPE have been aimed at for a long time.

However, the polymerization of vinyl substituted aromatics in thepresence of PPE was found to be prohibited or inhibited, which causeslower polymerization yields of the vinyl substituted aromatic monomerand more particularly when the PPE is used in a large amount there aresome cases where the polymerization does not progress at all.Accordingly, no substantial polymerization could be progressed unlessthe PPE was used in an amount as small as possible to make theconcentration of the vinyl substituted aromatic compound higher.

This phenomenon was especially observed in the case where a vinylsubstituted aromatic, and more particularly styrene, was polymerized inan aqueous dispersion in the presence of PPE and optionally a rubbercomponent. Several processes were proposed in the past such as thosedescribed in Japanese patent application No. 22069/67; Dutch patentapplication No. 6617529; French patent No. 1,551,503, using largeexcesses of styrene as to the PPE.

A common feature of all these processes was that in order to decreasethe styrene content of the polymerization product, it was necessary tolower polymerization yield. In the case of polymerization of e.g.styrene in a suspension system there was observed a phenomenon, thateven if the styrene content of the polymerization is intended to bedecreased by lowering the polymerization yield, a large amount ofunreacted styrene remains in the polymerization product.

The unreacted monomer relatively high in boiling point, which wascontained in such beads, was found to be difficultly removed by drying,with the result that a moulded article obtained from the polymerizationproduct was greatly injured in appearance and was also deteriorated inphysical properties.

In order to avoid these disadvantages, several remedies were proposed inthe past such as described in e.g. U.S. Pat. No. 3,862,263, proposing aprocess, in which a relatively small amount of a styrene compound issubstantially completely graft polymerized on PPE, optionally mixed withan elastomeric polymer, and as described in U.S. Pat. No. 4,287,321disclosing the preparation of PPE-poly(vinyl aromatic) compositions byoxidatively coupling a phenol dissolved in a basic reaction medium,comprising a vinyl aromatic compound in the presence of a manganesechelate catalyst, selectively extracting base-reactive by-products, andthen thermally polymerizing the vinyl aromatic compound.

As another remedy to avoid the hereinbefore described difficulties,processes were proposed for capping the starting PPE by conversion ofthe remaining free hydroxyl groups in said PPE with a material capableof reacting therewith to form inert substituents in a mutual solventsuch as aromatic solvents like toluene, benzene.

Typical examples of such capping agents include acid halides, acidanhydrides or ketenes as disclosed in e.g. European patent applicationsNos. 0261574 and 0264623 and U.S. Pat. Nos. 4,048,143; 4,189,417;4,156,773; and 4,165,422.

Although this capping process was known in principle for some time, arather extensive research for improved and more economical embodimentshas still continued, an important part of the efforts being directed tothe application of improved alternative capping agents, as appears e.g.from German patent application No. 3238930, U.S. Pat. No. 4,743,661 andthe International patent application WO 83/02117.

Although some of the hereinbefore described processes could indeedprovide some progress in the art, there remained a strong need forpolymer blends which are obtainable by an economically attractiveprocess for polymerization of a vinyl substituted aromatic monomer inthe presence of relatively large amounts of PPE, to be incorporated inthe final polymer blends, showing the desired improved characteristicssuch as high temperature rigidity, and more particularly final polymerblends representing interpenetrating networks.

More particularly there is still a need for an economical manufacturingprocess for the preparation of modified PPE, which can successfully beapplied for the manufacture of blends of polymer of vinyl substitutedaromatic monomers and said modified PPE in order to get modified hightemperature rigid compositions aimed at. With the term "modified hightemperature rigid compositions" as used throughout the presentspecification are meant compositions, which show a higher glasstransition temperature (Tg) as compared with conventional compositionsand as a consequence a higher Vicat softening point e.g. measuredaccording to Vicat B DIN 53460.

As a result of extensive research and experimentation there was nowsurprisingly found a process for the manufacture of modifiedpolyphenylene ether or structurally related polymers, comprising thereaction of a compound of the formula: ##STR1## wherein R₁, R₂, R₃ andR₄ are independently a hydrogen atom, a halogen atom or an alkyl groupor an alkoxy group, both being optionally substituted by halogen, cyano,hydroxy or phenyl group, and having 12 or less carbon atoms, an aryloxyor arylalkoxy group, optionally substituted by halogen, hydroxy or cyanogroup and having 12 or less carbon atoms, a di(alkyl)amino group or adi(alkanoyl)amido group, wherein the alkyl groups have 12 or less carbonatoms, and wherein R₁, R₂, R₃ and R₄ may represent different or the samegroups in one repeating unit, and n represents an integer having a valueof at least 50 and more preferably 100 to 500, with a non-cyclic acidanhydride of the general formula: ##STR2## wherein R₅ and R₆ eachindependently may represent an alkyl, alkenyl, aryl (preferably phenyl)or aralkyl (preferably aryl lower alkyl) group, containing from 1 to 12carbon atoms and optionally being substituted by hydroxy, halogen andpreferably bromine, alkyl containing 1-4 carbon atoms, or a free oresterified carboxyl group, in the presence of a catalyst of the formula:##STR3## wherein R₉ and R₁₀ both represent in general non-electronwithdrawing groups such as alkyl groups containing from 1 to 4 carbonatoms, optionally substituted by at most one phenyl group and whereinthe symbols R₇ and R₈ represent hydrogen, halogen or lower alkyl, whileR₉ and R₁₀ may represent different or the same groups in one molecule,and in a vinyl substituted aromatic monomer as solvent.

According to preferred embodiments of this process of the presentinvention the symbols R₁, R₂, R₃ and R₄ in formula I are selected fromhydrogen or an alkyl containing from 1 to 4 carbon atoms and morepreferably from hydrogen and methyl. Most preferably R₁ and R₄ bothrepresent methyl and R₂ and R₃ both represent hydrogen.

Typical examples of the polyphenylene ether or structurally relatedpolymers to be applied for the process of the present invention, includepoly-2,6-dimethyl-1,4-phenylene ether; poly-2,6-diethyl-1,4-phenyleneether; poly-2,6-dipropyl-1,4-phenylene ether;poly-2-methyl-6-allyl-1,4-phenylene ether;poly-ditert-butyl-dimethoxy-1,4-phenylene ether;poly-2,6-dichloromethyl-1,4-phenylene ether,poly-2,6-dibromomethyl-1,4-phenylene ether;poly-2,6-di(2-chloroethyl)-1,4-phenylene ether;poly-2,6-ditolyl-1,4-phenylene ether; poly-2,6-dichloro-1,4-phenyleneether; poly-2,6-diphenyl-1,4-phenylene ether andpoly-2,5-dimethyl-1,4-phenylene ether.

Preferred examples of compounds of the formula II, are those wherein R₅and R₆ represent the same group. More preferably acetic anhydride,benzoic anhydride, bromoacetic anhydride, fumaric acid anhydride and thelike are used and most preferably acetic anhydride or bromoaceticanhydride is used.

In the catalyst according to formula III, the symbols R₉ and R₁₀preferably represent both methyl groups or ethyl groups, whereas R₇ andR₈ preferably represent hydrogen, chlorine or methyl. Most preferablyN,N-dimethyl-4-amino pyridine (DMAP) is used as catalyst.

It will be appreciated that in the vinyl substituted aromatic monomeroptionally one or more elastomeric homopolymers or copolymers may beincluded. More particularly homopolymers or copolymers of a vinylsubstituted aromatic monomer and a conjugated diene monomer may beincluded. More particularly block copolymers AB or ABA comprising ablock of vinyl-substituted aromatic monomer (A) and a block ofconjugated diene (B) such as polystyrene and polybutadiene orpolyisoprene blocks may be used. More preferably partially hydrogenatedand/or modified block copolymers of a vinyl-substituted aromatic monomerand conjugated diene may be included.

Suitable examples of elastomeric polymers may be selected frompolybutadiene, polyisoprene (including natural rubber), polychloroprene,butadiene-styrene random or block copolymers, prepared by emulsion orsolution polymerization, polyisoprene-styrene random or blockcopolymers. Such included copolymer may improve the impact strength.

The vinyl substituted aromatic monomer may be selected from the groupconsisting of styrene, alphamethylstyrene, 2,4-dichlorostyrene,p-methoxystyrene, p-nitrostyrene, p-methylstyrene, 3,4-dimethylstyrene,m-tert-butylstyrene, p-dodecylstyrene, p-phenylstyrene,p-acetoxystyrene, divinylbenzene, p-aminostyrene,p-(chloromethyl)-styrene, m-cyanostyrene, o-hydroxystyrene,p-vinylbenzoic acid, alpha-propylstyrene, alpha-undecylstyrene,o-methyl-alpha-methylstyrene, m-methyl-alpha-methylstyrene,p-methyl-alpha-methylstyrene, p-methoxy-alpha-methylstyrene,p-cyano-alphamethylstyrene, m-bromo-alpha-methylstyrene,p-chloroalpha-methylstyrene and 1,1-diphenylethylene or mixtures thereofof which styrene alone or predominantly styrene containing monomermixtures being preferred.

It will be appreciated that in the event that R₁, R₂, R₃ or R₄represents a substituent containing a hydroxyl group, a correspondingexcess amount of the non-cyclic acid anhydride is used.

The vinyl substituted aromatic monomer itself and more preferablystyrene, or mixtures of them is used as solvent for the preparation ofthe modified PPE or structurally related polymer. During this conversiona reaction temperature is applied in the range of from 0° to 60° C. andmore preferably from 10° to 30° C.

According to a preferred embodiment of the process of the presentinvention for preparation of capped PPE or structurally related polymer,an amount of 5-50% by weight of e.g. unmodified PPE calculated on theweight of the complete reaction mixture, is converted.

However, in principle higher concentrations of unmodified PPE orstructurally related polymer may be converted too, whereafter theobtained reaction mixture may be diluted with additional vinylsubstituted aromatic monomer to the desired concentration of PPE, beforestarting the polymerization process.

On the other hand, one can also prepare low concentration PPE solutionsin vinyl substituted aromatic monomer and remove a part of this monomerby evaporation to obtain the desired concentration of PPE.

More preferably unmodified PPE or a structurally related polymer is usedin the starting mixture in a concentration of 30-50% by weight.

With the term "unmodified PPE or structurally related polymers", as usedthroughout the present specification, are meant polymers, havingterminal free hydroxy groups.

During the conversion of unmodified PPE or structurally related polymer,the catalyst may be used in a concentration in the starting reactionmixture of from 0.0025-0.1% by weight and preferably of from 0.01 to0.075% by weight, calculated on the weight of the complete reactionmixture.

The non-cyclic acid anhydride according to formula II may be used in aconcentration in the starting reaction solution, e.g. in styrene, offrom 0.05 to 0.5% by weight and more preferably from 0.1 to 0.3% byweight, calculated on the weight of the complete reaction mixture.

It will be appreciated that according to the present conversion processof unmodified PPE or structurally related polymer, bearing terminal freehydroxy groups, modified PPE or structurally related polymer is quicklyand efficiently obtained as compared with prior art processes. Theproduct shows characteristic infrared absorption maxima, from which thecharacteristic maxima which normally may be attributed to the presenceof any free hydroxy group, have disappeared to a substantiallyneglectable level, whereas the other characteristic maxima, originallyfound for the starting PPE, being not attributable to hydroxy groups,have remained. Moreover, a novel characteristic Fourier transformedinfrared absorption maximum is found at about 1765 cm⁻¹, e.g. as shownin FIG. 1 for PPE converted with acetic anhydride, isolated byprecipitation in methanol, showing a maximum at 1764.98 cm⁻¹, ascompared with normal PPE.

It will be appreciated that another aspect of the present invention isformed by the use of the modified PPE or a structurally related polymerfor the manufacture of modified, high temperature rigid polymers ofvinyl substituted aromatics by means of several polymerization methods,dependent on the finally desired application of said compositions.

Accordingly the present invention is also relating to a process for themanufacture of heat stable modified poly(vinyl substituted aromatic)compositions, comprising the polymerization of a vinyl substitutedaromatic monomer in the presence of a modified polyphenylene ether or astructurally related polymer, obtainable by reaction of a compound ofthe formula: ##STR4## wherein R₁, R₂, R₃ and R₄ are as definedhereinbefore, with a compound of the formula: ##STR5## wherein R₅ and R₆are as defined hereinbefore in the presence of a catalyst of theformula: ##STR6## wherein R₇, R₈, R₉ and R₁₀ are as defined hereinbeforeand in a vinyl substituted aromatic monomer as solvent.

It will be appreciated by persons skilled in the art that such a processenables an economically very attractive manufacture of the desired vinylsubstituted aromatic polymers, modified by the incorporation of PPE or astructurally related polymer.

For example beads of modified polymers of vinyl substituted aromaticsmay be prepared by aqueous suspension polymerization. Such beads may beoptionally impregnated by a physically and/or chemically blowing agentduring or after the polymerization process. Such beads may be appliedfor e.g. injection moulding, extrusion etc., to prepare a great varietyof engineering plastics when non-impregnated beads are used, and may beapplied in impregnated expandable forms to prepare a great variety ofengineering foams.

It will be appreciated that the polymerization of the vinyl substitutedaromatic monomer, containing the modified (capped) PPE or structurallyrelated polymer may also be carried out as bulk polymerization,optionally in the presence of usual auxiliaries, such as fillers, fibresor non-woven webs, dyes, stabilizers or flame retardants, to form shapedarticles.

Especially the manufacture of thermoplastic matrix polymer compositions,having a specifically desired shape, was not possible up to now.Therefore, it is an unexpected advantage of the process of the presentinvention that such shaped thermoplastic matrix polymers are providednow.

It was found that the modified PPE or structurally related polymer couldbe incorporated in situ into the polymer compositions to be formedduring polymerization of the vinyl substituted aromatic in asufficiently effective amount and in an economically attractive way.More particularly the modified PPE or structurally related polymer couldbe incorporated in an economically attractive way, into beads ofpolymers of the vinyl substituted aromatics and more preferably styrene,which are formed during aqueous suspension polymerization of suchmonomers.

With the term "in a sufficiently effective amount" as used throughoutthe present specification, is meant to indicate that the modified PPE orstructurally related polymer can be incorporated in situ during thepreparation of these matrixpolymer blend beads of the polymer of vinylsubstituted aromatic to provide to them the desired heat stability. Forexample increase of Tg of the final beads of about 40° C. as comparedwith beads substantially free of PPE or structurally related polymer,when containing an amount of about 40% by weight of PPE or structurallyrelated polymer, calculated on the weight of the final matrixpolymerblend composition.

Preferably the modified PPE or structurally related polymer, and morepreferably PPE, obtained according to hereinbefore specified conversion,is subsequently used for incorporation into matrixpolymer blend beads,to be formed by means of aqueous suspension polymerization to be carriedout by methods known in principle.

The polymerization process may be carried out in any suitable reactorequipped with heating means and agitating means. The reaction mixture,obtained by the conversion of unmodified PPE or structurally relatedpolymer, is heated for a period of time and a temperature to cause thevinyl substituted aromatic monomer to polymerize. Generally temperaturesof from 80° C.-175° C. may be employed and preferably in the range offrom 90° to 130° C. for a period of 2 to 10 hours. If temperatures abovethe boiling point of vinyl substituted aromatic monomer are used or ifblowing agents have to be impregnated during polymerization pressurevessels should be used to prevent vaporization.

According to a preferred embodiment of the aqueous suspensionpolymerization, the amount of water may vary from 1 to 10 parts byweight, per part by weight of the reaction mixture containing themodified PPE or structurally related polymer and vinyl substitutedaromatic monomer(s) and preferably from 1 to 2 parts water per part byweight of the reaction mixture. The aqueous dispersion to be used mayoptionally contain a dispersion stabilizer and one or morepolymerization catalysts.

Examples of such dispersion stabilizers include polyvinyl alcohol,gelatine, agar, starch, glycerine, sodium salt of polyacrylic acid andpolymethacrylic acid, polyethylene glycol, hydroxyethyl cellulose,carboxymethyl cellulose, methyl cellulose, ethylene glycol,polyacrylamide and 1:1 copolymer of e.g. styrene and maleic anhydride.The amount of the dispersion stabilizer to be used is ordinarily from0.0001 to 3% by weight and preferably from 0.001 to 1.5% by weight andmore preferably 0.01 to 0.7% by weight, based on the weight of the waterused.

Typical examples of the polymerization catalysts include decanoylperoxide; benzoyl peroxide; lauryl peroxide; octanoyl peroxide; stearylperoxide; 3,5,5-trimethyl hexanoyl peroxide; tert-butyl perbenzoate;tert-butyl peracetate; tert-butyl perpivalate; diisopropylbenzenehydroperoxide; 2,5-dimethyl-2,5-di-tert-butyl peroxyhexane;di-tert-butyl peroxide; cyclohexanone peroxide; dicumyl peroxide;alpha,alpha'-azobisiso butyronitrile, tert-butyl peroxyisobutyrate andtert-butyl peroxylaurate.

These radical initiators are preferably high temperature decomposingtype catalysts or are used in the form of a combination of 2 or morecatalysts, e.g. a combination of a low temperature decomposing typecatalyst with a high temperature decomposing type catalyst. In case thecombination of a low temperature decomposition type catalyst with a hightemperature decomposing type catalyst is used, the polymerization iseffected initially at below about 90° C. and, after a certain extent ofpolymerization yield has been attained, the temperature of the system iselevated to carry out the polymerization substantially completely at ahigh temperature.

Preferred combinations of the catalysts used include combinations oflauroyl peroxide with dicumyl peroxide; lauroyl peroxide withdi-tert-butyl peroxide; lauroyl peroxide with tert-butyl peroxybenzoate;lauroyl peroxide with 2,5-dimethyl-2,5-di-tert-butyl peroxyhexane;lauroyl peroxide with benzoyl peroxide; 3,5,5-trimethylhexanoyl peroxidewith dicumyl peroxide; 3,5,5-trimethylhexanoyl peroxide with tert-butylperoxybenzoate; 3,5,5-trimethylhexanoyl peroxide with benzoyl peroxide;3,5,5-trimethylhexanoyl peroxide with di-tert-butyl peroxide; tert-butylperoxypivalate with di-tert-butyl peroxide; tert-butyl peroxypivalatewith dicumyl peroxide; tert-butyl peroxypivalate with tert-butylperoxybenzoate; 2,4-dichlorobenzoyl peroxide with tert-butylperoxybenzoate; 2,4-dichlorobenzoyl peroxide with dicumyl peroxide;2,4-dichlorobenzoyl peroxide with di-tert-butyl peroxide;2,4-dichlorobenzoyl peroxide with 2,5-dimethyl-2,5-di-tert-butyl hexane;octanoyl peroxide with dicumyl peroxide, octanoyl peroxide withdi-tert-butyl peroxide, and benzoylperoxide withdi-tert-butylperoxybenzoate.

In the present invention, the polymerization catalyst may be used in anamount suitable for polymerization of the vinyl substituted aromaticcompound. For adequate practice of the present invention, the catalystis used in an amount of 0.01 to 1% by weight, preferably 0.3 to 0.7% byweight, based on the weight of the fed monomers.

The obtained modified poly(vinyl substituted aromatic) and morepreferably polystyrene beads, containing the modified PPE orstructurally related polymer, may be impregnated with a blowing agent toprovide the desired expandable beads of modified polymer of vinylsubstituted aromatic during or after polymerization.

The invention is further illustrated by the following examples, howeverwithout restriction of its scope to these specific embodiments.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows infrared adsorption spectrum as measured in Example 1.

EXAMPLE 1

Several polyphenylene ethers (mol. weight in the range from Mn 20,000 toMn 30,000) were dissolved in styrene in about 1 hr at room temperature,in an amount of 30% by weight, based on the weight of the totalcomposition. Subsequently acetic anhydride andN,N-dimethyl-4-aminopyridine (DMAP) were added in amounts of 0.1% byweight and 0.01% by weight respectively, calculated on the weight oftotal reaction mixture. After 1 hr stirring at room temperature a smallsample of the reaction mixture was precipitated in methanol at roomtemperature and an infrared absorption spectrum was measured as depictedin FIG. 1, showing a characteristic absorption maximum at 1764.98 cm⁻¹.Hereafter the temperature was increased to 70° C. and water, containing0.2% by weight of Natrosol 250 G (Registered Trademark) (I.V.=350mPa/sec, 2% aqueous solution measured at 25° C.) of 70° C. was added.

Thereafter the obtained suspension was heated to 93° C. and radicalpolymerized during 5 hours in the presence of dibenzoylperoxide (DBPO),followed by subsequent reaction during three hours at 110° C.-120° C. inthe presence of tert-butylperoxybenzoate (TBPB).

Regular spherical beads were obtained, showing a Tg of about 135° C.These obtained beads were subsequently impregnated with a blowing agent.

EXAMPLE 2

Several polyphenylene ethers [poly(2,6-dimethyl-1,4-phenylene) ether]having a number average molecular weight Mn in the range of from 20,000to 30,000 were dissolved in styrene at room temperature to provide a 10%by weight solution and acetic anhydride and DMAP were added in amountsto give concentrations of 0.2% by weight and 0.05% by weightrespectively (calculated on the weight of the total reaction system).After stirring for one hour at room temperature the solution was heatedto 130° C. and prepolymerized for 1 hr.

The solution was then suspended in water containing 0.2% by weightNatrosol 250 G polymerized in the usual way.

This resulted in spherically round beads with a Tg of ±110° C.

An identical experiment was carried out, using 20% by weight of PPE,except for the pre-polymerization step. After heating to 130° C. thesolution was suspended, resulting also in transparent beads with a Tg of±120° C.

EXAMPLE 3

Polyphenylene ether (Mn=25,000) was dissolved in styrene at roomtemperature to provide a 40% by weight solution and acetic anhydride andDMAP were added in amounts to give concentrations of 0.4% by weight and0.11% by weight respectively calculated on the weight of total reactionmixture.

After 1 hr stirring at room temperature a woven fabric (Keflar 49,Registered Trademark) was added. Thereafter this sample was heated to140° C. and polymerized thermally. The matrix of the resulting compositehas a Tg of ±140° C.

EXAMPLE 4

In the same way as described in Example 2 polyphenylene ethers dissolvedin styrene were converted with benzoic anhydride and DMAP, followed bysuspension polymerization in water containing 0.2% by weight Natrosol250 G, resulting in spherically round beads with a Tg of ±110° C.

EXAMPLE 5

The same experiment of Example 2 was repeated using bromoaceticanhydride and DMAP, followed by suspension polymerization in watercontaining 0.4% by weight tricalciumphosphate resulting in sphericallyround beads with a Tg of ±110° C.

We claim:
 1. The process of incorporating a modified polyphenylene etherinto a poly (vinyl substituted aromatic) polymer by means of aqueouspolymerization comprising the free radical polymerization of a vinylsubstituted aromatic monomer in the presence of the modifiedpolyphenylene ether, obtained by a previous reaction of a compound ofthe formula: ##STR7## wherein R₁, R₂, R₃ and R₄ are independently ahydrogen atom, a halogen atom or an alkyl group or an alkoxy group, bothbeing optionally substituted by halogen, cyano, hydroxy or phenyl group,and having 12 or less carbon atoms, an aryloxy or arylalkoxy group,optionally substituted by halogen, hydroxy or cyano group and having 12or less carbon atoms, a di(alkyl)amino group or a di(alkanoyl)amidogroup, wherein the alkyl groups have 12 or less carbon atoms, andwherein R₁, R₂, R₃ and R₄ may represent different or the same groups inone repeating unit, and n represents an integer having a value of atleast 50, with a non-cyclic acid anhydride of the general formula:##STR8## wherein R₅ and R₆ each independently may represent an alkyl,alkenyl, aryl or aralkyl group, containing from 1 to 12 carbon atoms andoptionally being substituted by hydroxy, halogen, alkyl containing 1-4carbon atoms, or a free or esterified carboxyl group, in the presence ofa catalyst of the formula: ##STR9## wherein R₉ and R₁₀ both represent ingeneral non-electron withdrawing groups and wherein the symbols R₇ andR₈ represent hydrogen, halogen or lower alkyl, while R₇, R₈, R₉ and R₁₀may represent different or the same groups in one molecule, and in avinyl substituted aromatic monomer as solvent.
 2. Product obtained bythe process of claim 1.